Method of separating the constituents of gaseous mixtures



A. J. FAUSEK ET AL METHOD OF SEPARATING THE CONSTITUENTS Oct. 24, 1950 OF GASEOUS MIXTURES Original Filed Aug. 4, 1943 7 5 3 4 2 2 I 4 6 65 6 6 5 0 44 i I Fj w 4 A a w 5 A Q T 2 W 6 I Q b 6 a x 5 A C 5 4 6 3 6 5 4 ATTORNEY- Patented Oct. 24, 1950 METHOD OF SEPARATING THE CONSTITU- ENTS OF GASEOUS MIXTURES Arthur J. Fausek and Irwing F. Fausek, e Clayton, M0.

Original application August 4, 1943, Serial No.

497,302. Divided and this application January 19, 1945, Serial No. 573,600

4 Claims. (Cl. 62-1755) This invention relates generally to the separation of the constituents of gaseous mixtures, and more specifically to an improved method of separating the constituents of air by liquefaction and rectification, the predominant object of the invention being to provide an improved method of separating and recovering the constituents of air, in such condition of purity as is required for commercial purposes, in an efficient and economical manner.

The single view of the drawing illustrates diagrammatically an apparatus for carrying out the method of the invention.

In the drawing, wherein is shown for purposes of illustration, merely, one embodiment of an apparatus for carrying out the improved method, I designates a heat exchanger, the particular heat exchanger illustrated comprising an elongated, vertically disposed cylindrical shell 2 which includes a lower portion that provides a housing for a liquefier 3. the bottom of the liquefier portion of the shell 2 of the heat exchangerbeing provided with a closure 4 and the top of said shell being provided with a similar closure 5.

Disposed within the shell 2 of the heat exchanger i is a coil 5 which is connected at its upper end to an inlet conductor 7, high pressure air being conducted by said inlet conductor to said coil for passage therethrough within the shell 2. The lower portion of the coil 6 is connected to a manifold 8 which is associated with a conductor 9 that leads as an inlet conductor to an expansion engine it so that high pressure air which passes through said coil 6 is delivered to said expansion engine. Also, connected into the manifold 8, by a conductor it, is a coil I2 and a coil l3; said coils i2 and I3 being parts of the liquefier 3 and being connected at their lower ends into a manifold M. Connected to and extending from the manifold M is a conductor l5 which is provided with a valve i5 and leads to a mixing chamber I6, and extended from the expansion engine to said mixing chamber is the outlet conductor ill of said expansion engine ill. The mixing chamber l6 has associated therewith an outlet conductor H which leads therefrom to a primary receptacle l8 that forms a part of the column C of the apparatus and is located adjacent to the lower end thereof.

From the foregoing it is apparent that high pressure air enters the heat exchanger l by way of the inlet conductor 1 and passes through the coil 6 therein. Part of the air which passes through the coil 8 passes to the expansion engine ill by way of the conductor 9. and part of said air passes by way of the conductor II to and through the coils l2 and I3 of the liquefier 3 to the manifold l4, whence it passes, in the form of liquid as will presently appear herein, through the conductor IE to the mixing chamber is. Expanded air discharged from the expansion engine l0 likewise passes to the mixing chamber 16, but in the form of a gas, and the parts of air reaching the mixing chamber from the coils l2 and I3 and from the expansion engine are mixed in the mixing chamber and pass therefrom to the primary receptacle E8 of the column C of the apparatus.

A lower portion of the column C of the apparatus illustrated in the drawing constitutes a primary dephlegmator t9, the outer housing of which is provided by a lower portion of the cylindrical shell of said column C. The primary dephlegmator it includes an inner cylindrical shell 2! which is disposed throughout a major portion of its length, centrally within the shell 2!! of the column C, the lower portion of said inner shell 2! projecting out of the lower end of the column shell 20 and being extended some distance below the bottom thereof. .Arranged at the lower end of the shell 20 of the column C is a horizontal wall 22, said horizontal wall being provided with a centrally located opening through which the inner, cylindrical shell 2| extends, and outer and inner annular flanges formed on said'horizontal wall 22 being suitably secured to said outer and inner shells, respectively. Likewise, the lower end of the inner, cylindrical shell 2i is closed by a closure member 23 which is suitably secured thereto. The primary receptacle It, previously referred to herein, is of annular formation and surrounds the inner cylindrical shell 21!, the conductor ll, also previously referred to herein, being in communication with the annular chamber 18' of said primary receptacle.

Located above the horizontal wall '22, heretofore mentioned, is another horizontal wall 24 which is provided with upwardly and downwardly extended, circumferential flanges to which upper and lower portions of the shell 20 of the column C are secured by welding, or otherwise. The horizontal wall 24 is provided with an outer portion which is located between the walls of the outer shell 20 and the inner shell 2|, and this outer wall portion supports a plurality of vertical tubes 26 which are arranged in a pair of circular rows, one within the other.

At their upper ends the tubes 26 are secured by welding, or otherwise, to the bottom wall of a hollow head 28 whose interior provides an enclosed fluid-tight, gas-tight chamber 29, the upper portions of the tubes 26 being extended through openings formed through the bottom wallof the head 28 and communicating with the chamber 29 thereof. Additionally, the primary dephlegmator l9 includes a bank of inner tubes 38 which are disposed within the upper portion of the inner cylindrical shell 2| and are secured by welding, or otherwise, to the horizontal wall 24 and the bottom wall of the head 28, said tubes 30 communicating at their upper ends with the chamber 29 of the head 28 and having open lower ends which terminate at points located slightly below the horizontal wall 24. Supported by the head 28 and secured thereto by welding, or otherwise, to the top and bottom walls thereof is a centrally located tube 3|. The centrally located tube 3| projects upwardly above the top wall of the head 28 into a cavity 32 provided by an upwardly extended portion of said top wall of said head, and said centrally located tube 3| terminates at its lower end at a point located slightly above the horizontal wall 24.

Associated with the tubes 26 is a plurality of injection tubes 34 of less diameter than the bores of said tubes 26, there being one injection tube associated with each of the tubes 26 and each injection tube being extended upwardly into the lower portion of its associated tube 26. At their lower ends the injection tubes 34 extend through openings formed in wall portions of the primary receptacle l8 and communicate with the chamber l8 thereof. Also, the injection tubes extend through openings formed through the wall 22 at the bottom of the shell 20 of the column C.

An annular chamber 38 is defined by the horizontal walls 22 and 24, and by wall portions of the outer shell 28 and the inner shell 2|, and communicating with this chamber is a conductor 38 which is extended upwardly to an expansion valve 40. Also, arranged between the expansion valve 48 and the upper portion of the primary dephlegmator I9 is a series of spaced trays 4| which are arranged horizontally of the column C, said trays being provided with bubble cups 42. Certain of the trays 4| are provided with centrally supported, vertical tubes 43 which are open throughout their lengths, the upper end ofeach tube 43 being located slightly above the associated tray 4|, and the lower ends of the upper pair of tubes 43 opening into cup-shaped portions 44 of trays which are located beneath said tubes, while the lowermost tube 43 opens at its lower end into the cavity 32 at the top of the head 28.

The lower portion of the inner shell 2| provides a chamber 45 which may be aptly described as a secondary receptacle, and leading from this secondary receptacle is a conductor 41 which has connected thereto at its upper end a coil 48 that is suitably supported within the column C immediately above the expansion valve 40. Arranged above the coil 48 is a series of horizontal trays 50 which are constructed and arranged in accordance with the trays 4| previously described herein, in that said trays are provided with bubble cups and certain of said trays support tubes 52, the lower, elongated tube 52 opening at its lower end into a cavity 53 formed in the upper portion of the expansion valve 48. The upper end of the coil 48 is connected into a conductor 54 which is provided with a valve 55 and connects at its upper end into a conductor 56, said conductor 56 having its upper and lower ends extended into the column C at vertically spaced points.

conductor 15.

Arranged within the column C at the point where the upper and lower end portions of the conductor 56 enter said column, is a secondary dephlegmator 51 that includes a lower, horizontal wall 58 which is supported by the column, and an upper, hollow head 59 which is provided with an interior chamber 62. The secondary dephlegmator includes, also, a nest of vertical tubes 63 which are fixed at their opposite ends to the bottom wall of the head 59 and to the lower, horizontal wall 58, respectively, the tubes 63 being open throughout their lengths and communicating at their lower ends with the portion of the interior of the column C which is located below the lower, horizontal wall 58 of the secondary dephlegmator 51, and at their upper ends with the chamber 62 of the head 59. Located below the horizontal, lower wall of the secondary dephlegmator 51 is an expansion valve 64, said expansion valve being connected into the space above said lower wall 58 of said secondary dephlegmator 51 by a tube 65 which is shaped as shown in the drawing.

Connected to the head 59 of the second dephlegmator so that it communicates with the chamber 62 thereof, is a conductor 66 that is provided with a valve 61. When the operation of the improved method disclosed herein is described later it will be found that pure nitrogen flows through the conductor 66, and said conductor 66 has connected to it at its lower end a coil 68, portions of which are disposed within the liquefier 3 and within the heat exchanger I. The upper portion of the coil 68 is connected into a conductor 69 which leads pure nitrogen passing therethrough to its destination. Likewise, the top of the column C is closed by a head 10, and connected to said head. so that it communicates with the interior of the column, is a conductor 1| which is provided with a valve 12. The conductor 1| is connected into the lower end of the shell that provides the housing of the heat exchanger and the liquefier 3, and impure nitrogen flows from the top of the column, through the conductor 1| and into and upwardly through the housing of the liquefier 3 and heat exchanger I, outside of the coils therein, said impure nitrogen flowing from the top of the housing of the heat exchanger and liquefier to its destination, through a conductor 13, which is connected to the 'top closure 5 of said housing so that it communicates with the interior of said housing.

The heat exchanger I includes therein another coil 14, to the lower end of which is connected 2. The conductor 15 is made up of an assembly of pipes 15a, 15b, and 150, the pipe 15a being connected into the column C at a point adjacent to the top of the primary dephlegmator IS, the pipe 15b being connected into the column C at a point adjacent to said primary dephlegmator and immediately above the bottom wall thereofand into the pipe 15a, while the pipe serves to connect the pipe 15a to the coil 14. During operation of the apparatus pure oxygen flows through the conductor 15 and through the coil 14, said coil being connected at its upper end to a conductor 16 which serves to conduct pure oxygen from the coil 14 to its destination. Also. the pipes 15a and 15b are provided with valves 11 adapted for use in drawing from the column C either liquid oxygen, through the pipe 15b, or vaporous oxygen through the pipe 15a, or both liquid and vaporous oxygen.

In the operation of the apparatus described above, air under high pressure flows into the heat exchanger I through the conductor 7 and passes into and through the coil 6 to the manifold 8. From the manifold 8 part of the incomlng high pressure air passes through the conductor-8 to the expansion engine l and part thereof passes, by way of the conductor II, to and through the coils l2 and I3 of the liquefier 3. From the coils l2 and I3 of the'liquefier the high pressure air passes to the manifold 4 and therefrom by way of the conductor 5 to the mixing chamber I6. Likewise, air which passed to the expansion engine In by way of the conductor 9 is discharged from said expansion engine'in an expanded condition by way of the conductor l8, and this air is mixed with the air that flows into the mixing chamber through the conductor IS. The expanded air which passes to the mixing chamber |6 from the expansion engine is in a gaseous condition while the medium that passes to the mixing chamber from the liquefier 3 is in a liquid state, the change of the air from a gaseous state to a vaporous state being brought about in the liquefier 3, and partly in the heat exchanger wherein the temperature of the incoming air is very greatly reduced by passage through the housing of the liquefier and the heat exchanger, in contact with the tubes through which the air passes, of impure nitrogen of extremely low temperature which comes from the top of the column C of the apparatus.

The air which is mixed in the mixing chamber 6 is delivered by the conductor H to the primary receptacle I8 and this medium passes upwardly from said primary receptacle through the injection tubes 34 and is discharged upwardly into the tubes 26. These tubes 26 are extremely cold. being surrounded by a body of liquid oxygen 0, and therefore liquefaction of the air discharged into the tubes 26 by the injection tubes 34 is brought about within said tubes 26. As a result of such liquefaction of the medium passing upwardly through the tubes 26, liquid rich in oxygen collects on the inner faces of the tubes and flows downwardly of the tubes 26 through the spaces between the inner faces of the walls of said tubes 26 and the outer faces of the walls of said injection tubes 34', and is discharged from the lower ends thereof into the annular chamber 38 with which the lower open ends of said tubes 26 communicate.

The vapors which reach the upper ends of the tubes 26 are made up largely of impure nitrogen with a relatively small percentage of oxygen adhering thereto, and these vapors are discharged into the chamber 29 of the head 28 whence they move downwardly through the descending tubes 38 to the chamber provided in the lower portion of the inner shell 2| of the primary dephlegmator. The cold liquid and vapors that so gather in the chamber referred to are conducted therefrom by the conductor H to the coil 48 through which said coil said liquid and vapors pass so as to serve as a refrigerant.

Likewise, the liquid rich in oxygen that gathers in the chamber 38 passes upwardly therefrom through the conductor 39 to the expansion valve 40 where it is subjected to quick expansion. This liquid gathers on and in the various trays 4| until it reaches elevations which permit it to overflow into the tubes 43 and thus pass from tray to tray, said liquid finally passing through the lowermost tube 43 into the trap 32 at the top of the head 28 of the primary dephlegmator l9 wherein said liquid overflows into the tube 3| and is discharged into the chamber provided by the inner shell 2| and the horizontal wall 24. This liquid, which is substantially pure oxygen, builds up in the chamber referred to until it overflows the top of the inner shell 2| and fills the chamber between the inner and outer shells 28 and 2| to the approximate level of the top of the inner shell to provide the body of oxygen 0. During its passage downwardly of the column C the nitrogen associated with the liquid is separated therefrom by evaporation and this gaseous nitrogen flows upwardly through the column, passin through the bubble cups 42 of the trays 4'| and moving in contact with the cold coil 48 on its way.

The impure nitrogen which is conducted to the coil 4'8 by the conductor 47, passes from said coil by way of the conductor 54 and the liquid and gaseous portions of said nitrogen are separated in the conductor 56, the liquid nitrogen flowing from the lower end of said conductor 56 to build up and maintain the body of liquid nitrogen N which surrounds the tubes 63 of the secondary dephlegmator 51, and the upper end of the conductor 56 acting as a vent which discharges gaseous nitrogen into the upper portion of the column C at a point above the level of the body of liquid nitrogen N. This gaseous nitrogen that flows from the upper end of the conductor 56 flows from the top of the column through the conductor 1| and is discharged thereby into the lower end of the housing'of the liquefier 3 and heat exchanger I, said very cold impure gaseous nitrogen passing through said housing and acting as a refrigerant therein and flowing from said housing at the top thereof through the conductor 13. Preferably the tube 65 which conducts liquid nitrogen from the body of nitrogen N to the expansion valve 64 is shaped as shown, so

that the surface of said body of nitrogen will be maintained at a predetermined point, as illustrated. Also the upper return bend of said tube 65 is provided with a suitable vent 65 for escape of gas from said tube.

Liquid is drawn from the body N of nitrogen that surrounds the tubes 63 of the secondary dephlegmator 51 and is subjected to quick expansion at the expansion valve 64, said liquid being discharged downwardly and flowing from 1 tray to tray of the assembly of trays 50 in the manner previously explained ,in connection with the trays 4|. During such operation any oxygen which is still associated with the nitrogen is separated therefrom and passes downwardly of the column C and the nitrogen moves upwardly through the tubes 63 of the secondary dephlegmator 51 into the chamber 62 of the head 6| of said secondary dephlegmator. Likewise, any nitrogen which moves upwardly from the lower portion of the column C passes through the bubble cups 5| of the trays 58 and through said tubes 63 of the secondary dephlegmator 51 into the chamber 62 of the head 6| thereof. The gas within the chamber 62 is approximately nitrogen, and this gas is conducted from the column C by way of the conductor 66 and passes from said conductor into and through the coil 68, portions of which form parts of the liquefier 3 and the heat exchanger I, to the conductor 69.

The body of liquid oxygen 0 at the primary dephlegmator I9 is substantially pure oxygen and this oxygen is conducted away from the column C by the pipe assembly 15 for delivery to the coil 14 of the heat exchanger I, said oxygen being delivered by the coil 14 to the conductor I6. It is to be noted that the pipe 15a of the pipe assemtit 15 is tapped into the column 0 at a point heat exchanger by appropriate adjustment of the valves ll.

While only oxygen and nitrogen are mentioned heretofore in this specification as being parts of the atmosphere acted on by the apparatus, it is realized that such atmosphere includes as parts thereof argon and other gases. In the normal operation of the apparatus these additional gases are wasted with the impure nitrogen, although, if desired, argon may be recovered by tapping into the column C at the proper point and conducting the argon away from the column.

This is a division of an application filed in the names of Arthur J. Fausek and Irwing F. Fausek, on August 4, 1943, Serial No. 497,302, now U. S. Patent No. 2,492,932, issued December 27, 1949.

We claim:

1. The method of separating air under high pres ure into its constituents which comprises expanding a part of the compressed air, liquefying the remainder thereof, mixing the expanded and liquefied fractions together, rectifying and separating the mixture into bodies of crude nitrogen and crude oxygen, collecting and separating the said body of crude nitrogen into its liquid and gaseous phases, expanding a liquid portion thereof so that said liquid phase does not fall below a certain level, passing the gaseous remainder from said last-named expansion in indirect heatexchange relation with said unexpanded liquid phase to condense a portion of the said gaseous remainder, and using the said condensed portion as liquid reflux.

2'. The method of separating air under high pressure into its constituents which comprises expanding a part of the compressed air, liquefying the remainder thereof, mixing the expanded and liquefied fractions together, rectifying and separating the mixture into bodies of crude nitro gen and crude oxygen, expanding the crude oxygen and separating nitrogen therefrom, said nitrogen moving toward a point of recovery as gas, herein called the nitrogen current, collecting and separating the said body of crude nitrogen into its liquid and gaseous phases, expanding a liquid portion thereof so that said liquid phase does not fall below a certain level, combining the gaseous remainder from said last-named expansion with said nitrogen current, passing the nitrogen current in indirect heat-exchange relation with said unexpanded liquid phase to said recovery point, thereby condensing a portion of the said gaseous remainder, and using the said condensed portion as liquid reflux.

3. The method of separating air under high pressure into its constituents which comprises expanding a part of the compressed air, liquefying the remainder thereof, mixing the expanded and liquefied fractions together, rectifying and separating the mixture into bodies of crude nitrogen and crude oxygen, expanding the crude oxygen and separating nitrogen therefrom, said nitrogen moving toward a point of recovery as gas, herein called the nitrogen current, the liquid remainder moving toward theoxygen recovery point, collecting and separating the said body of crude nitrogen into its liquid and gaseous phases, expanding a liquid portion thereof so that said liquid phase does not fall below a certain level, combining the gaseous remainder from said lastnamed expansion with said nitrogen current, passing the nitrogen current in indirect heatexchange relation with said unexpanded liquid phase to said recovery point, while combining vaporous condensate resulting from said heatexchange step with the liquid resulting from the last-named expansion, and withdrawing nitrogen ai-fi oxygen from their respective points of recovery in indirect heat-exchange relation with the incoming compressed air.

4. The method of separating air under high pressure into its constituents which comprises expanding a part of the compressed air, liquefying the remainder thereof, mixing the expanded and liquefied fractions together, rectifying and separating the mixture into bodies of crude nitrogen and crude oxygen, expanding the crude oxygen and separating nitrogen therefrom, said nitrogen moving toward a point of recovery as gas, herein called the nitrogen current, the liquid remainder moving toward the oxygen recovery point, transferring the body of crude nitrogen in indirect heat-exchange relation with said nitrogen current to a collector where it is separated into its liquid and gaseous phases, removing the gaseous phase in indirect heat-exchange relation with the incoming compressed air initially to cool the latter, expanding a liquid portion of said liquidphase so that the latter does not fall below a certain level, combining the gaseous remainder from said last-named expansion with said nitrogen current, passing the nitrogen current in indirect heat-exchange relation with said unexpanded liquid phase to said recovery point, thereby condensing a portion of said gaseous remainder, combining this condensate with the liquid resulting from the last-named expansion, and withdrawing nitrogen and oxygen from their respective points of recovery in indirect heat-exchange relation with the incoming compressed air.

ARTHUR J. FAUSEK. IRW'ING F. FAUSEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date 981,748 Claude Jan. 17, 1911 1,678,485 Schlitt et al. July 24, 1928 1,771,197 Van Nuys et al July 22, 1930 1,830,157 De Baufre Nov. 3, 1931 1,968,518 Fraser July 31, 1934 2,195,976 Schlitt -JL Apr. 2, 1940 2,209,748 Schlitt July 30, 1940 

